Hydrocarbon oil additive



HYDROCARBON 01L ADDITIVE John P. McDermott, Springfield, N. 1., assignorto Esso Research and Engineering Company, a corporation of Delaware NoDrawing. Application December 22, 1951, Serial No. 263,020

11 Claims. (Cl. 25232.7)

The present invention relates to an improved class of additivesparticularly suitable for use in lubricating oils and to the compoundedmineral oils and other hydrocarbon products in which they are employed.

The application is a continuation-in-part of copending applicationSerial No. 100,741, filed on June 22, 1949, which has now issued as U.S. Patent 2,610,182 on September 9, 1952. 7

Modern developments in the design of internal combustion engines, withincreasing engine speeds and compression ratios, have imposed a severestrain on the lubricants employed. in particular, the crankcase oil israised to a high temperature and in the course of its circulationthrough the engine is repeatedly exposed to air under conditions highlyconducive to destructive oxidation. Oxidative breakdown of the oilresults in the formation of acidic products which corrode bearingsurfaces and do considerable harm to the engine generally. Furthermore,the metallic corrosion products have the effect of catalyzing furtheroxidative breakdown of the oil.

A number of compounds, more especially those of the phenolic type, areknown which exert an oxidation inhibiting effect when added to minerallubricating oils and other hydrocarbon products. Their effect is toprevent oxidative breakdown of the oil both on storage (long potentialreaction time and low temperature) and in use (short reaction time andhigh temperature). Although many antioxidants are known which stabilizethe oil adequately on storage, the majority of them tend to break downwith undesirable rapidity at high engine operating temperatures.

A principal object of the present invention is to provide a new class oflubricating oil antioxidants of good properties. Another object is toprovide an antioxidant which is stable and effective at relatively highengine temperatures. Other objects and advantages will be apparent fromthe following description.

It has now been found, according to the present invention, that thesalts formed by reacting thialdine or its homologs withsulfur-containing acids, such as sulfurized carboxylic acids,thiocarboxylic acids and the thio acids of phosphorus, are extremelyeffective antioxidants for hydrocarbon products liable to oxidation,especially mineral lubricating oils.

Thialdine, otherwise known as5,6-dihydro-2,4,6-trimethyl-l,3,5-dithiazine,- is represented by thestructural formula It is readily prepared by treating the condensationproduct of acetaldehyde and ammonia With hydrogen sulfide.

2,712,525 Patented July 5, 1955 Thialdine and the homologs of the samewhich are useful for the purposes of the present invention may berepresented by the general formula where R represents an alkyl group of1 to 10 carbon atoms. However, simple thialdine in which R is methyl ispreferred.

Sulfur-containing acids which may be used in forming the thialdine saltsof the present invention include sulfurized monoor dicarboxylicaliphatic acids which may be represented by the general formulas R 'COOHor COOH COOH where R represents a sulfurized aliphatic hydrocarbonradical having from 1 to 30 carbon atoms, preferably in the range of 4to 20 carbon atoms. The radical R may before sulfurization be saturatedor unsaturated, straight or branched chain, with or withoutcycloaliphatic, substituent chains, or it may be an alkyl substitutedcycloaliphatic nucleus. Examples of suitable acidsare the lower monoanddicarboxylic acids such as 'butyric, adipic, sebacic, and decanoicacids. Higher acids include lauric, oleic, linoleic, ricinoleic,palmitic, and stearic acids. Mixtures of acids, such as those obtainedbythe oxidation of parafiin Wax or other high molecular weight petroleumfractions, may also be used. The sulfurized acids may be prepared byheating the acid with elemental sulfur or with a sulfur halide. Examplesare sulfurizedoleic, sulfurized linoleic, and sulfurized oxidized waxacids. Thio acids of the formulas R'COSH (thiol acids), and R'CSSH(dithio acids), where R is a sulfurized or unsulfurized aliphaticradical having the same significance as above, may also be used. Xanthicacids (ROCSSH) and the like may also be used. The most preferredproducts, however, are those prepared from the thio acids of phosphorus,such as thiophosphorous and dithiophosphoric acids, both from the pointof view of effectiveness and from the point of view of ease ofpreparation. In general, partially esterified dithiophosphates orthiophosphites are preferred in making the monoor di-thialdine salt.These esterified compounds may be prepared by reacting an organichydroxy compound with a sulfide of phosphorus. Thus, a compound of theformula ROH, where R" represents an organic radical, may be treated withphosphorus pentasulfide in a molar ratio of 4:1, as shown below.

The diester dithiophosphoric acids are preferred as a general rule. Thecompound R"OI-I used for making the esters of thio acids of phosphorusmay be an alcohol,

such as a C2 to C20 aliphatic straight or branched chain or cyclicalcohol with or without substituent groups such as halogen, sulfur,amino, or nitro groups, or may be a phenol or an alkylated phenol, ahydroxy ester, hydroxy ether, etc. In general, the total number ofcarbon atoms in the group R should be from 2 to 30, preferably in therange of 4 to 20. Examples of suitable compounds are isopropyl alcohol,isobutyl alcohol, Z-ethylhexanol, iso-octyl alcohol, Ca Oxo alcohols,decyl alcohol, Lorol (CID-C16) alcohols, methylcyclohexyl alcohol,isopropyl cyclohexyl alcohol, mixed alcohols derived from paralfin waxor from chlorinated parafiin wax, phenol, p-cresol,2,4,6-triiosobutylphenol, p-isooctylphenol, ptert.-octylphenol,p-tert.-octylphenol sulfide. butyl lactate, a-hydroxy butyl stearate,the various glycol ethers known as Cellosolves, such as the monobutylether of ethylene glycol, etc.

The thialdine and homologous salts of the present invention may bereadily formed by contacting the thialdine compound with thesulfur-containing acid at room temperature'. Since heat is evolved, thereaction is preferably conducted in the presence of an inert solvent andby contacting the reactants gradually. Suitable solvents includechloroform, carbon tetrachloride, ethylene dichloride, benzene, and thelike.

The following examples illustrate the preparation and testing of variousthialdine salts according to this invention, but it is to be understoodthat these examples do not limit the scope of the invention in any way.

Example I.-Preparatin of thialdine di-nonyl di-thiophosphate A mixtureof 115.2 grams (0.8 mol) of C9 0x0 alcohol and 44.4 grams (0.2 mol) ofP285 was heated at 110 C. for 45 minutes with rapid stirring in a1-liter, 3-necked flask equipped with a stirrer, thermometer, and refluxcondenser. The resultant acid was then filtered and blown with nitrogenfor minutes.

i A solution of 95.5 grams (0.25 mol) of this product (di-nonyldi-thiophosphoric acid) in 100 cc. of CHCls was added dropwise over aperiod of minutes to a solution of 40.8 grams (0.25 mol) of thialdine in300 cc. of CHC13, maintaining the temperature below C. After stirringfor an additional hour at room temperature, the product was filtered andplaced on a steam bath k to remove the solvent. A viscous brown liquidwas obtained, which upon analysis was found to contain 5.5% phosphorus,22.1% sulfur, and 2.4% nitrogen.

Example 2.Preparati0n of thialdine di-methylcyclohexyl di-thiophosphateDi-methylcyclohexyl di-thiophosphoric acid was prepared by the methoddescribed in Example 1. using 114 grams (1 mol) of methylcyclohexanoland 55.5 grams (0.25 mol) of P2S5.

The thialdine salt was also prepared by the method described in Example1, using 96.6 grams 0.3 mol) of methylcyclohexyl thiophosphoric acid and49.0 grams (0.3 mol) of thialdine. A brown tacky solid was obtainedwhich upon analysis was found to contain 6.0% phosphorus, 24.5% sulfur,and 2.1% nitrogen.

Example 3.Preparati0n 0f thialdine di-sulfurized oleyl di-thiophosphateDi-sulfurized oleyl di-thiophosphoric acid was prepared by the methoddescribed in Example 1, using Example 4.Preparation of thialdinesulfurized oleate A mixture of 113 grams (0.4 mol) of oleic acid and12.8 grams (0.4 mol) of sulfur was heated for 1% hours at C.

The thialdine salt was prepared as described in Example 1. using 94.4grams (0.3 mol) of sulfurized oleic acid and 49.0 grams (0.3 mol) ofthialdine. A dark red liquid was obtained which upon analysis was foundto contain 18.5% sulfur and 2.5% nitrogen.

Example 5.--Preparati0n of thialdine oleate Thialdine oleate wasprepared substantially in accordance with the procedure of Example 4using 113 grams (0.4 mol) of oleic acid and 65.2 grams (0.4 mol) ofthialdine. An amber viscous liquid was obtained which upon analysis wasfound to contain 9.9% sulfur and 2.3% nitrogen.

These five products were then tested in the laboratory for theirinhibiting action against the corrosion of lead in copper-lead bearings,as shown in the following examples.

Example 6 In this test theadditives were blended in 0.25% by weightconcentration in an extracted Mid-continent oil of S. A. E. 20 grade andcomparative tests run on these blends and on a sample of the unblendedoil. The test was conducted as follows:

500 cc. of the oil was placed in a glass oxidation tube 13 inches longand 2% inches in diameter, fitted at the bottom with a /4 inch air inlettube perforated to facilitate air distribution. The oxidation tube wasthen immersed in a heating bath so that the oil temperature wasmaintained at 325 F. throughout the test. Two quarter sections ofautomotive bearings of copper-lead alloy, of known weight and having atotal surface area of 25 sq. cms., were attached to opposite sides of astainless steel rod which was then immersed in the test oil and rotatedat 600 R. P. M., thus providing sufiicient agitation of the oil duringthe test. Air was then blown through the oil at the rate of 2 cu. ft.per hour. At the end of each four-hour period, the bearings wereremoved, washed with naphtha, and weighed to determine the amount ofloss by corrosion. The bearings were then repolished (to increase theseverity of the test), reweighed and then subjected to the test foradditional four-hour periods in like manner. The results are given inthe following table as corrosion life, which indicates the number ofhours required for the hearings to lose 100 mgs. in weight, determinedby interpolation of the data obtained in the various periods.

The following data show that the salts of sulfur-containing acids wereelfective oxidation and corrosion inhibitors. The salt of anunsulfurized carboxylic acid, however. was quite inefiective under theconditions employed in this test.

Corrosion L'fe Thialdine Salt 1 (Hours) None (Base oil only) Dlnonyldl-thiophosphate (Ex. 1) Di(znethylcyclohexyl) di-thiophosphate (ExDi(sulfuri7.ed oleyl) di-thlophosphate (Ex. 3)..." Sulfurized cleate(Ex. 4) Oleate (Ex. 5)

Example 7 Weight Loss Oil per Bearing Base oil alone 9 Blend From thepreceding examples it will be evident that the thialdine salts ofsulfur-containing acids are effective antioxidants for lubricating oils.

As previously stated, any of the alkyl homologs of thialdine may beemployed although thialdine itself is preferred. The acid radical may bethat of a long chain thio acid such as oleic, palmitic or stearic thioacids, as heretofore mentioned. Sulfur-containing acids are preferred inthe carboxylic acid class, and these may be readily prepared, forexample, by heating the acid with elemental sulfur or with a sulfurhalide.

The additives may be blended in the oil in amounts of from about 0.02 toby weight, 0.1 to 2% being the preferred range. For load-bearingpurposes quantities of 2 to 15% may be used. For handling and storage,concentrates containing in the range of about 15 to 50% or more may beprepared. These may be added to base stocks to give blends of thedesired concentration.

In addition to the additives of this invention there may also be addedto the oil other conventional additives including detergent typeadditives, such as metal soaps, metal petroleum sulfonates, metalphenates, metal alcoholates, metal alkyl phenol sulfides, and the like.Examples of such additional additives are barium tert.-octyl phenolsulfide, calcium tert.-amyl phenol sulfide, cadmium or nickel oleates,calcium phenyl stearate, aluminum naphthenate, and zinc methylcyclohexylthiophosphate.

The lubricating oil base stocks used may be straight mineral lubricatingoils or distillates derived from any suitable or desired crudes, or, ifdesired, blended oils may be employed. The oils may have been subjectedto any conventional refining treatment such as acid, alkali and/ or claytreatment, or solvent extraction. Synthetic oils such as those preparedby the polymerization of olefins or by the Fischer-Tropsch synthesis mayalternatively be employed, alone, mixed, or in combination with mineraloils.

Further types of additives which may be present if desired include dyes,pour point depressants, heat thickened fatty oils, sulfurized fattyoils, organo-metallic compounds, sludge dispersers, thickeners,viscosity index improvers, oiliness agents, voltolized fats, waxes oroils, and colloidal solids such as graphite or zinc oxide, etc. Solventsand assisting agents such as esters, ketones, alcohols, aldehydes, andhalogenated or nitrated hydro carbons may also be employed wherenecessary or desirable.

Particularly suitable assisting agents are the Ca and higher alcohols(preferably C8 to C12) such as lauryl and stearyl alcohols, and the 0x0alcohols of corresponding chain length.

In addition to being employed in lubricants, the additives of thepresent invention may also be employed in other hydrocarbon productssusceptible to oxidative breakdown. Among these may be mentioned motorfuels, mineral oil base hydraulic fluids, torque converter fluids,cutting oils, flushing oils, turbine oils, transformer oils, industrialoils and process oils, natural and synthetic hydrocarbon rubbers, andthe like. They may also be used in gear lubricants, greases, and inother products containing hydrocarbon oils as ingredients.

What is claimed is:

l. A mineral oil composition having incorporated therein in the range ofabout 0.02 to by weight of the salt formed by reacting a thialdine-typecompound of the general formula where R is a C1 to C10 alkyl radical,with a sulfur-containing acid selected from the group consisting of (1)carboxylic acids of the general formula R'(COOH)n where R is a C1 to C30sulfurized aliphatic hydrocarbon radical, and n is an integer of from 1to 2, and (2) esters of thiophosphorous and di-thiophosphoric acids inwhich at least one of the hydrogen atoms is replaced by an organicradical containing from 2 to 30 carbon atoms and is selected from thegroup consisting of alkyl, sulfurized alkyl, aryl, aralkyl, alkaryl andcycloalkyl radicals.

2. A composition as in claim 1 wherein said thialdinetype compound isthialdine.

3. A composition as in claim 2 wherein said carboxylic acid issulfurized oleic acid.

4. A composition as in claim 2 wherein said ester of dithiophosphoricacid is dinonyl dithiophosphoric acid.

5. A composition as in claim 2 wherein said ester of dithiophosphoricacid is di-methyl cyclohexyl dithiophosphoric acid.

6. A composition as in claim 2 wherein said ester of saiddithiophosphoric acid is di-(sulfurized oleyl)dithiophosphoric acid.

7. A composition as in claim 1 comprising a mineral lubricant base stockand in the range of about 0.02 to 5% by weight of said salt.

8. An oil concentrate consisting of a mineral lubricating oil and in therange of about 15 to 50% by Weight of the salt of claim 1.

9. A composition as in claim 1 wherein said R radical has in the rangeof 4 to 20 carbon atoms.

10. A composition as in claim 1 wherein said acid is dithiophosphoricacid having both hydrogen atoms replaced by said organic radicals.

11. A composition as in claim 10 wherein said organic radicals have inthe range of 4 to 20 carbon atoms.

i CH-R No references cited.

1. A MINERAL OIL COMPOSITION HAVING INCORPORATED THEREIN IN THE RANGE OFABOUT 0.02 TO 50% BY WEIGHT OF THE SALT FORMED BY REACTING ATHIALDINE-TYPE COMPOUND OF THE GENERAL FORMULA